FDA Issues Caution on Magnesium Sulfate Use in Pregnant Women

Summary: This week the U.S. Food and Drug Administration (FDA) issued an alert announcing that women taking magnesium sulfate injections to prevent preterm labor should take it no more than 5 to 7 days total, because prolonged in-utero use can increase a baby's risk of low calcium levels and bone fractures.

Magnesium sulfate has FDA approval to prevent seizures in preeclampsia (high blood pressure and protein in the urine) as well as to control seizures in eclampsia, which is the rare but life-threatening result of untreated preeclampsia. The FDA has not approved its use for preventing preterm labor, and in light of its new findings, it discourages such use.

Based on 18 case reports as well as epidemiologic studies, the FDA has determined that there is a relation between "skeletal abnormalities in neonates" and in utero exposure to magnesium sulfate. In the case studies, the average duration of in-utero exposure to magnesium sulfate was 9.6 weeks. Among the other studies, one found a statistically significant increase in bone abnormalities with in-utero exposure to magnesium sulfate for more than 7 days, compared to those exposed for less than 3 days.

The FDA will now require a warning on the magnesium sulfate drug label; it is also changing the Teratogenic Effects of the drug (which rates potential harm to the developing baby) from Pregnancy Category A (that adequate and well-controlled studies have failed to demonstrate a risk to the fetus in the first trimester of pregnancy, and there is no evidence of risk in later trimesters) to Pregnancy Category D (there is positive evidence of human fetal risk, but the potential benefits from using the drug in pregnant women may be acceptable in certain situations despite its risks).

As always, women should communicate closely with their healthcare providers to determine the best treatment for them. But for those who hope to avoid taking magnesium sulfate, given these new found risks, a diet high in fiber and increased exercise may help stave off preeclampsia and preterm labor, all together.

Would you be willing to discuss alternative treatments with your doctor?

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Carolyn Buchanan

B.C. (before children), Carolyn was trained as a journalist — a generalist journalist. Now as a parent, she experiences news differently. What was once an item of passing interest, i.e. "Toy Train Runs on Lead Paint" or "Midnight Release Planned for Latest Power Rangers Movie" now consumes her life. Still she trains her eye to find the family relevance in everything new, and that's what she endeavors to share with you here. As a parent, and a writer for What to Expect, she will be your family-news filter (with a personal twist).

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